Process for preparing polymers of acrylamide with ethylenically unsaturated sulfines



United States Patent PROCESS FOR PREPAliING POLYMERS 0F ACRYL- E WITHETHYLENICALLY UNSATURATED SULFINES Frederick E. Baiiey, Jr., and EdwardM. La Combe,

Charleston, W. Va., assignors to Union Carbide Corporation, acorporation of New York No Drawing. Filed Aug. 10, 1961, Ser. No.130,482

Claims. (Cl. 26079.7)

This invention relates to a method of preparing novel, normally solid,water-soluble polymers of acrylamide with certain alpha-ethylenicallyunsaturated sulfines, i.e. sulfonium compounds possessing a terminalethylenic unsaturation; said novel polymers being disclosed and claimedin copending application Serial No. 327,092, filed November 29, 1963,which is of common assignee. These novel polymers are of particularutility as flocculants for flocculation of the disperse phase of aqueousanionic suspensions, as disclosed and claimed in United States Patent3,214,370 which is also of common assignee.

More particularly, the novel polymers with which this invention isconcerned include copolymers containing, in polymerized form and on atheoretical monomer basis, from about 20 to about 95 mole percent andpreferably from about 40 to about 70 mole percent of acrylamide, andfrom about 5 to about 80 mole percent and preferably from about 30 toabout 60 mole percent of an alphaethyl-enically unsaturated sulfine ofthe general formula:

wherein R designates either a hydrogen atom or a methyl radical; Rdesignates a saturated aliphatic hydrocarbon radical containing from 1to 4 and preferably from 2 to 3 carbon atoms, such radical morepreferably being unsubstituted in the position adjacent to the oxygenatom to which it is directly connected; R" designates an alkyl radicalcontaining from 1 to 4 and preferably from 1 to 2 carbon atoms, Rdesignates either a methyl or carboxymethyl (-CH COOH) radical; Xdesignates a halogen atom, such as a bromine, iodine or chlorine atom,or a methyl sulfate (OSO CH radical, and specifically designates achlorine atom when R designates a carboxymethyl radical; and mdesignates an integer of from 1 to 2. Moreover, in those instances whenm is 1, the

sulfonium radical it X is preferably attached to that carbon atom of theradical designated by R which is farthest from the adjacent oxygen atom,i.e., the carbon atom in the 1-position. When m is 2, the sulfoniumradicals are preferably attached to vicinal carbon atoms of the radicaldesignated by R, and more preferably to those vicinal carbon atoms ofthe radical which are farthest from the adjacent oxygen atoms, i.e., thecarbon atoms in the 1,2-position. In addition, when m is 2, R morepreferably contains at least 3 carbon atoms.

As illustrative of the alpha-ethylenically unsaturated sulfines which,in polymerized form, are a component of 7 the polymers of thisinvention, there can be mentioned:

acryloxymethyldimethylsulfonium methylsulfate,(2-ac-ryloxyethyl)dimethylsulfonium methylsulfate, (Z-acryloxyethyldimethylsulfonium bromide, (2-acryloxyethyl)dimethylsulfonium iodide,(Z-acryloxyethyl)methylethylsulfonium methylsulfate,(2-acryloxyethyl)methylbutylsulfonium methylsulfate, (3-acryloxypropyl)dimethylsulfonium methylsulfate, (4-acryloxybutyl)dimethylsulfoniummethylsulfate, (Z-methacryloxyethyl)dimethylsulfonium methylsulfate,(acryloxyrnethyl) carboxymethylmethylsulfonium chloride,(2-acryloxyethyl) carboxyrnethylmethylsulfonium chloride,(2-acryloxyethyl)carboxymethylethylsulfonium chloride, 2-acryloxyethyl)carboxymethylbutylsulfonium chloride, (3 -acryloxypropyl)carboxymethylmethylsulfonium chloride, (4-acryloxybutyl) carboxymethylmethylsulfonium chloride, (Z-methacryloxyethyl)carboxymethylmethylsulfonium chloride,3-acryloxypropyl1,2-bis(dimethylsulfonium) di(methylsulfate,3anethacryloxyptropyl-l,2-bis (dimethylsulfonitlm) di (methylsulfate)4-acryloXybutyl-1,2-bis(dimethylsulfonium) di(methylsulfate),4-methacryloxybutyl-1,2-bis(dimethylsulfonium) di(methylsulfate) 3-acryloxypropyl-1 ,2-bis (carboxymethylmethylsulfonium) dichloride,4-methacryloxybutyl-1,2-bis(carboxymethylmethylsulfonium) dichloride,etc.

The preferred sulfine monomers are the compounds represented by theformulae:

wherein R, R", R' and X are as defined above, and R"" designates asaturated aliphatic hydrocarbon radical containing from 2 to 3 carbonatoms.

This invention also contemplates the production and use of a terploymercontaining, in polymerized form and on a theoretical monomer basis, fromabout 20 to about 95 mole percent of acrylamide and from about 5 toabout mole percent of a mixture comprised of at least 50 mole percent ofan alpha-ethylenically unsaturated sulfine as defined above, togetherwith an alpha-ethylenically unsaturated thioether represented by theformula:

wherein R, R, R" and m are as defined above. As illustrative of suchalpha-ethylenically unsaturated thioethers, there can be mentioned:

Thus, the polymers of this invention are characterized by recurringunits represented by the structures:

L C 132-- C J O: NH

the copolymers consisting essentially of recurring units having thefirst two structures, while the terpolymers contain all three recurringunits.

The novel polymers of this invention can be produced by severaldifferent techniques. For example, the alphaethylenically unsaturatedsulfine can be obtained initially in monomeric form, and subsequentlypolymerized, v together with acrylamide, so as to produce a copolymerthereof, or in the additional presence of an alpha-ethylenicallyunsaturated thioether, so as to produce terpolymers thereof. To thisend, when desired initially in monomeric form, the alpha-ethylenicallyunsaturated sulfine can be obtained by reacting an alpha-ethylenicallyunsaturated thio-ether with an alkylating agent in accordance with theequation:

wherein R, R, R, R, X and m are as defined above. Reactions between athio-ether and an alkylating agent are in general discussed, forinstance, by H. Gilman in Organic Chemistry, vol. 1, 2nd ed., J. Wileyand Sons, N.Y. (1948) page 867, such teachings being incorporated hereinby reference. Concordant therewith, by way of illustration, thealkylation can be carried out by bringing the thio-ether and thealkylating agent into reactive admixture, in a suitable solvent ordiluent, if desired, at a temperature of from about 25 C. or slightlylower, up to about 90 C. to 100 C. or slightly higher. In addition, asmall amount of a conventional polymerization inhibitor, such ashydroquinone, or the like, is preferably incorporated in the reactionmixture. As typical of the alkylating agents which can be employed inthis regard, there can be mentioned dimethyl sulfate, methyl halidessuch as methyl bromide, methyl iodide and methyl chloride, 'chloroaceticacid, etc. Moreover, the reaction is preferably carried out in a diluentwhich is a solvent for the thio-ether, but a non-solvent for theresulting sulfine product, such as benzene, isopropyl ether, etc. Thesulfine product can then be separated and recovered in any convenientmanner.

The novel copolymers of this invention can thereafter be obtained bypolymerizing a mixture of acrylamide and the alpha-ethylenicallyunsaturated sulfine, in amounts corresponding approximately to thoseamounts hereinabove described in connection with the polymercomposition, i.e., from about 0.2 to about 20 moles and preferably fromabout 0.6 to about 2.5 moles of acrylamide per mole of sulfine, incontact with a catalytic amount of a free-radical polymerizationcatalyst or initiator. Typical free-radical polymerization catalystsinclude, for instance, azo compounds, such asazo-1,1'-diisobutyronitrile, dimethyl azo-2,2-diisobutyrate,azo-2,2-bis-(2,4-dimethylvaleronitrile), azo-2,2'-diisobutyramide andthe like; peroxides, such as hydrogen peroxide, sodium peroxide,peracetic acid, acetyl peroxide, benzoyl peroxide, potassium persulfate,calcium percarbonate and the like; alkylborons such as tributylboron, orthe like; etc. The catalyst is ordinarily incorporated in thepolymerization mixture in a concentration of from about 0.01 to about 5percent or more by weight, and preferably from about 0.2 to about 2percent by weight, based upon the weight of the monomers, although anycatalytic amount thereof can be utilized.

The polymerization is generally effected by bringing the monomers intocontact with the catalyst at a temperature of from about l0 C. orslightly lower, to about C. or slightly higher, accompanied by heatingor cooling as needed to maintain the temperature at the desired level.The time for the polymerization will depend on a variety of factors,such as the nature of the catalyst and monomers, the reactiontemperature, etc., and can vary over a wide range. For example, asuitable reaction time lies in the range of from about 1 hour to about200 hours, although any period suflicient to produce a polymeric productcan be employed. In addition, the polymerization can be carried outunder atmospheric, superatmospheric, or subatmospheric pressures, asdesired.

Preferably, the polymerization is carried out in diluent which is asolvent for the monomers, and in which the polymer product is insoluble.However, other polymerization techniques, such as bulk, or emulsionpolymerizations, etc., are also applicable. Moreover, it hasunexpectedly been found in this connection that especially good resultsare obtained by carrying out the polymerization using as the preferreddiluent, either acetone, acetonitrile, an acetone-acetonitrile mixturecontaining either component in a proportion of from about 1 to about 99percent by weight, or a constant boiling methyl acetatemethanol mixture,and by dissolving the monomers in such diluent in a concentration offrom about 5 to about '50 percent and preferably from about 5 to about30 percent by weight of total monomer based upon the total weight of thepolymerization charge. When conducted 'in this manner, the resultingpolymer is ordinarily obtained as an exceptionally high molecularweight, granular product which is conveniently handled, readilydissolved in water and which is particularly effective as a flocculantas herein described. In contrast therewith, polymer products of likechemical constituency, produced, however, in water ordimethylformamide,were obtained in the form of a clear gel which isuseful as a flocculant, but which was difiicult to agglomerate andhandle, while similar products, produced in benzene, heptane andethylene dichloride were generally of lower molecular weight and lesseffective in subsequent use as a fiocculant.

Upon completion of the polymerization, the polymer product can berecovered in any convenient manner, such as by filtration,centrifugation, etc. The polymer product, it is to be noted, isgenerally insoluble in conventional organic solvents, including those inwhich the monomers are soluble. The reaction product can also beemployed directly in many uses for the polymer, obviating the recoveryof the polymer per se.

In an alternative manner to the polymerization technique describedabove, the alkylation of the alphaethylenically unsaturated thio-etherand the polymerization of the monomers can be carried out in oneoperation by incorporating the alkylating agent in a polymerizationmixture containing from about 0.2 to about moles and preferably fromabout 0.6 to about 2.5 moles of acrylamide per mole of the thio-ether.Moreover, in such a procedure, the reactants must be employed in a ratioof at least about 0.5 mole, and preferably at least about 1 mole, up toabout 5 or more moles of the alkylating agent per thio-ether radical,{SR3-, of the thio-ether. The polymerization reaction and the recoveryof the resulting polymer is carried out as otherwise described above,with similar unexpected advantages accruing when the polymerization iscarried out using the preferred diluents described above. In thisconnection, it is to be noted that the terpolymers of this invention areobtained as products when there is employed less than a stoichiometricamount of alkylating agent with regard to the amount of thioetherpresent. In addition, the novel polymers of this invention can also beprepared by reacting the alkylating agent with an initially formedcopolymer of acrylamide and the thio-ether, the alkylation and initialpolymerization, as well as the recovery of the polymer product, alsobeing carried out as otherwise described above.

The novel polymers of this invention are solid, watersoluble compounds,and when produced by polymerization techniques utilizing the preferreddiluents described above, are obtained as granular, readilywater-soluble products having a reduced viscosity of from about 0.1 toabout 5 and preferably from 0.5 to 2, when measured at a temperature ofC. from an 0.5 molar aqueous sodium acetate solution containing 0.2 gramof polymer in 100 milliliters of solution. The term reduced viscosity iswell known in the polymer art and designates a value obtained bydividing the specific viscosity of a solution of the polymer by theconcentration of the polymer in solution, the concentration beingmeasured in grams of polymer per 100 milliliters of solvent. Thespecific viscosity is obtained by dividing the difference between theviscosity of the polymer solution and the viscosity of the solvent bythe viscosity of the solvent. The reduced viscosity of a polymer isregarded as a measure of the molecular weight of the polymer, withhigher values indicating higher molecular weights. Moreover, in the caseof a polyelectrolyte, such as the polymers of this invention, thereduced viscosity values are best obtained from a dilute aqueous saltsolution.

The polymer products of this invention find utility in a wide variety ofapplications. They can, for example, be used to produce films suitablefor use as packaging and coatings. It has been found that the polymerscan also be effectively employed as flocculants in the treatment ofaqueous anionic suspensions, wherein the dispersion of solid matter isstabilized by a negative change. This is especially true of the polymersproduced by polymerization techniques using the preferred diluentsdescribed above. Illustrative of the suspensions which can beflocculated in accordance with this invention there can be mentionedaqueous dispersions or slurries of silica, carbon, clay, biologicallytreated industrial wastes, such as textile mill wastes, etc., sewagesludge, white water, i.e. the effluent from paper-making machines usedin the con ventional manufacture of paper products which contains asuspension of paper-making fibers and which also contains a suspensionof fillers and/or pigments such as titanium dioxide and calciumcarbonate, etc., and the like. The polymers have in fact been found tobe especially effective in the treatment of sewage sludge, and can beemployed in this connection to treat raw sludge, digested or partiallydigested sludge, digested sludge elutriant, etc., i.e., at any of thevarious stages of conventional sewage treatment. In this manner, thepresent invention provides a distinct advantage over the use of manyconventional flocculants.

The polymers of this invention are employed as flocculant-s, as furtherprescribed by the invention, by admixing one or more of them in thesuspension for which flocculation is desired in a concentration whichcan vary broadly in the range of from about 0.01 to about 5 percent byweight of the polymer(s) based upon the weight of the solid dispersedphase. Preferably, polymer concentrations of from about 0.1 to about 2.5percent by weight are employed. The optimum concentration of polymer mayvary, of course, depending upon the suspension being flocculated, themolecular weight of the polymer, etc., and can readily be determined byone skilled in the art in light of this disclosure.

The polymer can be incorporated in the suspension in solid form anddissolved therein or, preferably, introduced as an aqueous solution.Stock solutions of the polymer are most conveniently prepared andutilized in this connection, preferably containing from about 0.25 toabout 5 percent by weight of polymer in water. Solutions containinghigher polymer concentrations can also be prepared, limited, forpractical purposes, only by the increasing viscosity of the solution asthe molecular weight and/0r concentration of the polymer increases. Anyother convenient manner of incorporation and admixing the polymer in thesuspension can also be utilized, as can any flocculating quantity of thepolymer. The flocculation thus effected is evidenced, for example, by ahigh rate of dewatering and rapid settling of the suspended solids.

The invention can be illustrated further by the following specificexamples of its practice. In the examples, the reduced viscosity valuesindicated for the polymers were measured at a temperature of 30 C. from0.5 molar aqueous sodium acetate solution of polymer containing 0.2 gramof polymer in milliliters of solution.

Example I A 300 cc. Pyrex bottle was charged with 8 grams ofZ-methylthioethyl acrylate, 12 grams of acrylamide, 100 grams of dryacetonitrile and 0.2 gram of azodiisobutyronitrile. The bottle wasflushed with nitrogen, capped and placed in a revolving, constanttemperature water bath at a temperature of 50 C. for a period of 20hours. An acrylamide/2-methylthioethyl acrylate copolymer was formed asa suspension in acetonitrile. The copolymer contained, in polymerizedform, and on a theoretic-a1 monomer basis, approximately 25 mole percentof the acrylate. A solution of 7 grams of dimethyl sulfate in 100 gramsof dry acetonitrile was then added to the suspension in the bottle,whereupon the bottle was returned to the revolving bath for anadditional period of 20 hours at a temperature of 50 C. The amount ofdimethyl sulfate employed was suflicient to convert essentially all ofthe polymerized Z-methylthioethyl acrylate units to the corresponding,polymerized form of 2- (acryloxyethyl)dimethylsulfonium methylsulfateunits, so that an acrylamide/Z-(acryloxyethyl)dimethylsulfoniummethylsulfate copolymer was formed as a suspension in acetonitrile. Thecopolymer contained, in polymerized form and on a theoretical monomerbasis, approximately 40 mole percent of the sulfonium compound and 60mole percent of acrylamide. The polymer suspension was then washed withdry acetone and subsequently filtered to recover the polymer.Thereafter, the polymer was dried at a temperature of 40 C. for a periodof 16 hours. In this manner, 26 grams of polymer were obtained as awhite powder. The polymer had a reduced viscosity of 0.68.

Example II (A) A polymer having approximately the same chem- Weight, wasobtained in a manner similar to that described in Example I, usingone-half the quantity of each reactant. Thus, 4 grams ofZ-methylthioethyl acrylate was initially polymerized with 6 grams ofacrylamide in 50 grams of dry acetonitrile by contacting the monomermixture with 0.1 gram of azodiisobutyronitrile at a temperature of 50 C.for a period of 16 hours. The acrylamide/ 2-methylthioethyl acrylatecopolymer suspension thereby formed was washed with isopropyl ether andfiltered to recover the polymer, which was then dried at a temperatureof 50 C. for a period of 16 hours. The copolymer, containing, inpolymerized form and on a theoretical monomer basis, approximately 26mole percent of the acrylate, was thereafter brought into reactiveadmixture with 3.5 grams of dimethyl sulfate in 100 grams of dryacetonitrile at a temperature of 50 C. for a period of 20 hours. Theamount of dimethyl sulfate employed was sufficient to convertessentially all of the polymerized 2- methylthioethyl acrylate units tothe corresponding, polymerized form of2-(acryloxyethyl)dimethylsulfonium methylsulfate units, so that anacrylamide/Z-(acryloxyethyl)dimethylsulfonium methylsulfate copolymerwas formed as a suspension in acetonitrile. The resulting copolymercontained, in polymerized form and on a theoretical monomer basis,approximately 40 mole percent of the sulfonium compounds and 60 molepercent of acrylamide. The polymer suspension was then washed withisopropyl ether and subsequently filtered to recover the polymer.Thereafter, the polymer was dried at a temperature of 50 C. for a periodof 16 hours. In this manner, 12 grams of polymer were obtained as awhite powder. The polymer had a reduced viscosity of 0.57.

(B) In similar manner to that described above in this example, 4 gramsof 2-methylthioethyl acrylate was initially polymerized with 6 grams ofacrylamide in 50 grams of dry acetonitrile by contacting the monomermixture with 0.2 gram of azodiisobutyronitrile at a temperature of 50 C.for a period of 20 hours. To the acrylamide/2- methylthioethyl acrylatecopolymer suspension thereby formed, 3.5 grams of dimethylsulfate weresubsequently introduced and brought into reactive admixture therewith ata temperature of 50 C. for a period of 20 hours. The amount of dimethylsulfate employed was suflicient to convert essentially all of thepolymerized 2-methylthioethyl acrylate units to the corresponding,polymerized form of 2-(acryloxyethyl)dimethylsulfonium methylsulfateunits, so that an acrylamide/2-(acryloxyethyl)dimethylsulfoniummethylsulfate copolymer was formed as a slurry in acetonitrile. Theresulting copolymer contained, in polymerized form and on a theoreticalmonomer basis, approximately 40 mole percent of the sulfonium compoundand 60 mole percent of acrylamide. The polymer slurry was then dilutedwith acetone and subsequently filtered to recover the polymer.Thereafter, the polymer was dried at a temperature of 50 C. for a periodof 16 hours. In this manner, 12.5 grams of polymer were obtained at awhite powder. The polymer had a reduced viscosity of 0.25.

Example 111 A 300 cc. Pyrex bottle was charged with 25 grams ofacrylamide, 25 grams of Z-(acryloxyethyl)dimethylsulfoniummethylsulfate, 120 grams of dry acetonitrile and 0.5 gram ofazodiisobutyronitrile. The bottle was flushed with nitrogen, capped andplaced in a revolving, constant temperature water bath at a temperatureof 50 C. for a period of 18 hours. An acrylamide/Z-(acryloxyethyl)dimethylsulfonium methylsulfate copolymer was formed as a suspension inacetonitrile. The copolymer contained, in polymerized form and on atheoretical monomer basis, approximately 80 mole percent of acrylamideand 20 mole percent of Z-(acryloxyethyl)dimethylsulfonium methylsulfate.The polymer suspension was then washed with isopropyl ether andsubsequently filtered to recover the polymer. There after, the polymerwas dried at a temperature of 50 C. for a rxeriod of 20 hours. In thismanner, 50 grams of polymer were obtained as a white powder. The polymerhad a reduced viscosity of 1.7 and was found by analysis to containabout 12 percent by weight of sulfur. The experiment was repeated inidentical manner, and a similar copolymer was obtained as a product. Thepolymer differed only in molecular weight, having a reduced viscosity of1.0. The two polymers were then blended together to form the productemployed as a fiocculant as indicated below.

Example IV A 500 cc., 4-neck, fiat Pyrex flask, fitted with a glassstirrer, thermometer and condenser, was charged with 15 grams ofacrylamide, 10 grams of 2-methylthioethyl acrylate, 9 grams ofdimethylsulfate, 200 grams of dry acetonitrile and 0.25 gram oftributylboron. The reactants were stirred under a positive nitrogenpressure, with the flask immersed in a constant temperature water bathat a temperature of C., for a period of minutes. An additional drop oftributylboron was added to the contents of the flask, after which theflask was allowed to remain in the bath, accompanied by continuedstirring, for a further period of 1.5 hours. A polymer was formed as aslurry of increasing thickness, whereupon an additional 100 grams of dryacetonitrile were introduced into the flask. The slurry was then heatedto a temperature of C., with stirring, over a period of 2 hours, allowedto stand overnight, and finally reheated to a temperature of 50 C., withstirring, over a period of 6 hours. The slurry was then washed withacetone and filtered to recover the polymer. Thereafter, the polymer wasdried at a temperature of 50 C. for a period of 16 hours. In thismanner, about 34 grams of anacrylamide/Z-(acryloxyethyl)dimethylsulfonium methylsulfate copolymerwere obtained as a white powder. The polymer contained, in polymerizedform and on a theoretical monomer basis, approximately 25 mole percentof the sulfonium compound and mole percent of acrylamide.

Example V A 300 cc. Pyrex bottle was charged with 3 grams of acrylamide,3 grams of 2-(acryloxyethyl)carboxymethylmethylsulfonium chloride, 12grams of dry acetonitrile and 0.06 gram of azodiisobutyronitrile. Thebottle was flushed with nitrogen, capped and placed in a revolving,constant temperature water bath at a temperature of 50 C. for a periodof 18 hours. An acrylamide/2-(acryloxyethyl)carboxymethylmethylsulfoniumchloride copolymer was formed as a suspension in acetonitrile. Thecopolymer contained, in polymerized form and on a theoretical monomerbasis, approximately mole per cent of acrylamide and 15 mole percent ofthe sulfonium compound. The polymer suspension was then washed withacetone and subsequently filtered to recover the polymer. Thereafter,the polymer was dried at a temperature of 50 C. for a period of 16hours. In this manner, 4.7 grams of polymer were obtained as a whitepowder. The polymer had a reduced viscosity of 2.08, and was found byanalysis to contain about 5.3 percent by weight of chlorine.

Example VI A 300 cc. Pyrex bottle was charged with 6 grams ofacrylamide, 2 grams of 2,3-bis(methylthio)propyl methacrylate, 2.3 gramsof dimethyl sulfate, 0.08 gram of azodiisobutyronitrile and 40 grams ofdry acetonitrile. The bottle was flushed with nitrogen, capped andplaced in a revolving, constant temperature water bath at a temperatureof 50 C. for a period of 62 hours. An acrylamide/ 3 acryloxypropyl 1,2bis(dimethylsulfonium) di(methylsulfate) copolymer was formed as asuspension in acetonitrile. The copolymer container, in polymerized formand on a theoretical monomer basis, approximately 92 mole percent ofacrylamide and 8 mole percent of the sulfonium compound. The polymersuspension was then washed with isopropanol and subsequently filtered torecover the polymer. Thereafter, the polymer was dried at a temperatureof 50 C. for a period of 16 hours. In this manner, 9.5 grams of polymerwere obtained as a white granular powder.

Example VII A 300 cc. Pyrex bottle was charged with 3 grams ofacrylamide, 2 gram of 2-(acryloxyethyl)carboxymethylmethylsulfoniumchloride, grams of dry acetone and 0.05 gram of azodiisobutyronitrile.The bottle was flushed with nitrogen, capped and placed in a revolving,constant temperature water bath at a temperature of 50 C. for a periodof 19 hours. An acrylamide/2-(acryloxyethyl)carboxymethylmethylsulfoniumchloride copolymer was formed as a suspension in acetone. The copolymercontaned, in polymerized form and on a theoretical monomer basis,approximately 85 mole percent of acrylamide and mole percent of thesulfouium compound. The polymer suspension was then washed with heptane,and filtered to recover the polymer. Thereafter, the polymer was driedat a temperature of 40 C. for a period of hours. In this manner, 4.8grams of polymer were obtained as a white powder. The polymer had areduced viscosity of 1.96.

Example VIII In this example, various polymers of this invention wereevaluated as flocculating agents in connection with the flocculation ofpigment-containing white water suspensions. The evaluation was conductedas follows. A synthetic white water was prepared by cutting bleachedsulfite pulp into 4-inch squares. The cut pulp was soaked in water andbeaten for a period of 1 hour in a Valley laboratory beater to aconsistency of 1.7 percent. A 1- quart aliquot of the beaten pulp,containing 15 grams of pulp fiber in suspension in water, was removedand diluted to 15 gallons with additional water, whereupon 1.5 grams ofpigment were also added to the suspension, giving a total solids contentof 0.029 percent by weight. One-liter aliquots, containing 0.3 gram ofsolids, were then removed from the suspension, and were treated withvarying amounts of the polymer being evaluated by admixing each aliquotof the suspension with an aqueous solution of the polymer for a shortperiod. The eflectiveness of the polymer as a flocculant was determinedby measuring the rate of filtration of water from the polymer-treatedsuspension in the following manner. An inverted Buchner funnelcontaining No. 1 Whatman filter paper was cOnnected to an evacuatedflask, serving as a source of constant vacuum, and immersed for oneminute in the treated polymer suspension. The filtrate was collected ina filter flask and measured.

The results obtained are tabulated below in Tables A, B and C. In TableA, the data tabulated was obtained from experiments conducted usingkaolinite clay as the sole pigment component of the synthetic whitewater; in Table B, the data tabulated was obtained from experimentsconducted using titanium dioxide as the sole pigment component of thesynthetic white water; and in Table C, the data tabulated was obtainedfrom experiments conducted using titanium dioxide as the sole pigmentcomponent of the synthetic white water. The polymers evaluated were thepolymers produced as described above in Examples IIA, III and VII. Forcomparison, experiments were also conducted employing in one instance,as the polymer, a commercially available polyacrylarnide 'flocculant,and in another instance, substituting for the polymer, anothercommercially available flocculant, viz., alum, Al (SO .l8H O. Inaddition, a control experiment was conducted in which no flocculant wasemployed.

In the tables, the concentration of flocculant is indicated in percentby weight of polymer based upon the weight of pulp in the suspension.The pH is that of the treated suspension. The filtration rateis.tabulated in cubic mm 10 timeters per minute, i.e., the volume offiltrate collected under standard conditions in one minute. Forconvenience and clarity the filtration rate has also been converted to afiltration rate ratio according to the formula:

Filtration rate of fioeculant-treated white water" Filtration rate ofuntreated white Water :filtration rate ratio wherein the denominatorrepresents the filtration rate obtained in the control experiment inwhich no flocculant was employed. A ratio greater than 1 indicates thatflocculation has been engendered, increasing in eflectiveness as theratio increases.

TABLE A Flocoulant Employed Concentration pH Filtration Filtration ofFlocculant Rate Ratio TABLE B ;FlocculantEmployed Concentration pI-IFiltration Filtration of Flocculant Rate Ratio TABLE 0 FloeculantEmployed Concentration pH Filtration Filtration of Floceulant Rate RatioNone 8. 4 1.0 Polyacrylamide 0. 33 8.4 110 0. 69 Polymer of Ex. VII.0.033 8. 4 380 2. 4 Do 0.33 8. 4 270 1. 7 3. 3 8. 4 375 2. 3 33 8. 4 600. 37

The superior eflectivness of the polymers of this invention as aflocculant is readily apparent from the above tables. It can also beseen that the optimum amount of the flocculant, insofar as effectivenessas a fiocculant is concerned, will vary depending upon the particularpolymer employed as well as upon the suspension being treated, and thatan excessive amount of flocculant may have an adverse, deflocculatingeffect. Thus, as indicated previously, the optimum amount of flocculantcan readily be determined by one skilled in the art in light of thisdisclosure. In addition, it can be seen that, unlike certainconventional flocculants, the polymers of this invention are effectiveas flocculants in both acidic and basic en vironments.

Example IX In this example, the polymer of this invention produced asdescribed above in Example I, was evaluated as a flocculating agent inconnection with the flocculation of a digested sewage sludge suspensioncontaining 6 percent total solids, obtained from a commercial sewagetreatment plant. The evaluation was conducted as follows. A 0.5 percentsolution of the polymer was prepared by sifting 5 grams of the polymerinto 995 grams of water, following by admixture with a Lightnin mixer ata speed of about 1750 rpm. for a period of one hour. The polymerappearing readily soluble under these low shear conditions. To appraisethe shear stability of the polymer under high shear conditions and toinsure dissolution, 500

grams (one-half) of the polymer sol'ution'was mixed further in a WaringBlendor at a speed of about 15,000 r.p.m. for a period of 4 minutes. Thedigested sewage sludge suspension was then treated with varying amountsof polymer which, in one instance had been subjected to only low shearmixing, and in another instance, to both low and high shear mixing, byadding 150 milliliter aliquots of aqueous polymer solution to 300 gramsaliquots of the sewage sludge suspension in a 500 milliliter graduatedcylinder. The contents of the cylinder were initially mixed by invertingthe cylinder 30 times, whereupon the contents were transferred to a 600milliliter beaker and stirred therein for a period of 5 minutes using apaddle-blade stirrer rotating at a speed of about 100 r.p.m. Theeffectiveness of the polymer as a fiocculant was determined by measuringthe rate of filtration of water from the polymertreated suspensions inthe following manner. An inverted Buchner funnel, sawed off flush to theperforated disc, was fitted with #40 Whatman filter paper and connectedto an evacuated flask, serving as a source of constant vacuum (30 to 40millimeters of mercury). The funnel was then immersed for 30 seconds inthe treated suspension in an inverted position and thereafter allowed todrain in an upright position for another 30 seconds, thus simulating acommercial vacuum drum filtration operation. The filtrate was collectedin a filter flask and measured.

The results obtained are tabulated below in Table D. In the table, thedesignation (a) indicates the polymer was subjected to only low shearmixing during dissolution as described above in this example; thedesignation (b) indicates the polymer was subjected to both low shearmixing and then to high shear mixing as also described above in thisexample. The concentration of flocculant is indicated in percent byweight of polymer based upon the weight of sewage sludge solids. Thefiltration rate is tabulated in cubic centimeters per minute, i.e., thevolume of filtrate collected under standard conditions in one minute bythe procedure indicated above. For comparison, an experiment wasconducted, substituting for the polymer a commercially available ferricchloride flocculant. A control experiment was also conducted in which noflocculant was employed.

TABLE D Flocculant Employed Concentration of Filtration Rate FlocculantThe improved flocculating effectiveness of the polymer of this inventionis again apparent from the above table. In similar manner, the polymerproduct of Example VI is also employed elfectively as a flocculant.

Example X admixture with a Lightnin mixer at a speed of about 900 r.p.m.for a period of 2 hours. To insure dissolution of the polymer, thesolution was mixed further under high shear conditions in a WaringBlendor at a speed of about 15,000 r.p.m. for a period of 3 minutes.Aliquots of the polymer solution were then diluted with additional waterto a total volume of 60 milliliters and added to'200 gram aliquots of adigested sewage sludge suspension containing 5 percent total solids byweight, obtained from a commercial sewage treatment plant. After beingstirred gently for a period of 1 minute, the polymer-treated sewagesludge was poured into a vacuum filtration apparatus consisting of a 9centimeter diameter Buchner funnel equipped with No. 4 Whatman filterpaper and-adapted to a 250 milliliter graduated cylinder, which was inturn connected to a water aspirator, serving as a vacuum source. Thevolume of filtrate obtained from the polymer-treated sewage sludge andcollected in the graduated cylinder was recorded at frequent intervalsuntil the dewatering of the sewage sludge ceased. This procedure wasrepeated using various proportions of flocculant to sewage sludge untila maximum filtration rate was attained. The concentration of flocculantwas calculated as a percentage ratio of the weight of polymer to theweight of the sludges solid fraction on a dry basis. In addition, forcontrol purposes, an experiment was conducted in which no flocculant wasemployed.

The data obtained were interpreted according to the relationshipsdeveloped by Dr. P. Coackley as described in Biological Treatment ofSewage and Industrial Wastes, J. McCabe, ed., vol. 2, ReinholdPublishing Corp., New York, '1958, pp. 270-91. The relationships derivedexpress the filterability of the flocculated sludge in terms of thespecific resistance of the sludge. Relative specific resistances can bedetermined from data collected by the Buchner funnel technique ashereinabove described. When the filtration pressure, filtrate viscosity,solids content of the sludge, and filter area are all held constant, thespecific resistances of various sludges are proportional to theirfiltration gradients. The filtration gradient is expressed as the slopeof the plot of t/ V vs. V, where t is time in seconds and V is filtratevolume in milliliters. The filterability is inversely proportional tothe specific resistance; hence, it is also inversely proportional to thefiltration gradient.

This technique provides a convenient means of comparing theeffectiveness of various fiocculants. Since a major commercialapplication of flocculants will involve their use in conjunction withrotary vacuum filters, the various flocculants can be compared on thebasis of the anticipated increase in filter yield (lb. dry flocculatedsolids/ sq. ft. of filter area/ hr.) accomplished by flocculation of thesludge. The filter yield has been reported to be inversely proportionalto the square root of the specific resistance of the filter cake. Sincespecific resistance is proportional to filtration gradient under theconditions of this procedure, fil ter yield is also inverselyproportional to the square root of the filtration gradient.

The data obtained, and the relationships derived therefrom, aretabulated below in Table E. In the table the optimum concentrationindicates the lowest concentration of flocculant at which a maximum rateof filtration was attained, and is indicated in percent by weight ofpolymer based upon the weight of sewage sludge solids; the filtrationgradient, designated in seconds/centimeter, indicates the slope of theplot of tv/ V, wherein t and V are as de fined above. For convenienceand comparison, the filtration gradient has also been converted to afiltration improvement factor according to the formula Filtrationgradient of flocculant-treated sludge Filtration gradient offlocculant-untreated sludge =filtration improvement factor l3 wasemployed. The filter yield improvement factor is the square root of thefiltration improvement factor.

14 alkyl radical containing from 1 to 4 carbon atoms, R designates amember selected from the group consisting TABLE E Optimum FiltrationFiltration Filter Yield Flocculant Concentration Gradient ImprovementImprovement Factor actor Polymer 01 Example HA." 2. 4 0.00044 1, 140 34Polymer of Example 111,. 2. 4 0.023 22 5 None 0.50

Example XI of the methyl and carboxymethyl radicals, X designates Aseries of experiments were conducted in a manner similar to thatdescribed above in Example X, with the following exception, viz., thatonly a portion of the stock solution of each polymer tested wassubjected to high shear mixing in a Waring Blendor as indicated above.The data obtained, and the relationships derived therefrom, aretabulated below in Tables F and G as described above in connection withTable E. The data tabulated in Table F were obtained from experimentsemploying a digested sewage sludge suspension containing 3 percent totalsolids by weight; the data tabulated in Table G were obtained fromexperiments employing a digested sewage sludge suspension containingabout 6 percent total solids by weight; both sludge samples beingobtained from a commercial sewage treatment plant. In the tables, thedata tabulated in column A were obtained from experiments in which thepolymer solution was subjected to only low shear mixing during itspreparation. The data tabulated in column B were obtained fromexperiments in which the polymer solution was also subjected to highshear mixing during its preparation.

a member selected from the group consisting of the bromine, iodine andchlorine atoms and the methyl sulfate radical, such that X designates achlorine atom where R designates a carboxymethyl radical, and mdesignates an integer of from 1 to 2, said copolymer containing, inpolymerized form and on a theoretical monomer basis, from about 20 toabout 95 mole percent of acrylamide and from about 80 to about 5 molepercent of said ethylenically unsaturated sulfine and having a reducedviscosity of from about 0.1 to about 5 as measured at a temperature of30 C from a 0.5 molar aqueous sodium acetate solution containing 0.2gram of said copolymer in 100 milliliters of said solution, whichprocess comprises reacting said acrylamide and said ethylenicallyunsaturated sulfine in admixture in a mole ratio of from about 0.2 toabout 20 moles of said acrylamide per mole of said sulfine, in a solventselected from the group consisting of acetone, acetonitrile and mixturesthereof, at a temperature of from about 10 C. to about 120 C and incontact with a free-radical polymerization catalyst.

TABLE F Flocculant Optimum Filtration Optimum Filtration ConcentrationGradient Concentration Gradient Polymer of Example V l 3. 3 0. 00045 3.3 0.00159 Polymer of Example VII. 1 2. 5 0.00047 2. 5 0.00138 None. 0,31

1 Higher concentrations were not tested.

TABLE G Flocculant Optimum Filtration Optimum Filtration ConcentrationGradient Concentration Gradient Polymer of Example IIB 1. 1 0.00011 0.70.00040 Polymer of Example I- 1.4 0.00021 0.9 0.00037 Polymer of ExampleIV 1. 8 0. 00010 1. 4 0. 00039 None. 0.25

The polymers of this invention have also been found 2. The methodaccording to claim 1 wherein the ethylefiective as fiocculating agentsin connection with the enically unsaturated sulfine is2-(acryloxyethyDdimethylflocculation of aqueous suspensions containingclay, carbon black and silica.

What is claimed is:

1. A process for the production of a solid, granular high-molecularweight copolymer of acrylamide and an alpha-ethylenically unsaturatedsulfine of the general formula:

R 111 wherein R designates a member selected from the group consistingof the hydrogen atom and the methyl radical, R designates a saturatedaliphatic hydrocarbon radical containing from 1 to 4 carbon atoms, R"designates an wherein R designates a member selected from the groupconsisting of the hydrogen atom and the methyl radical, R designates asaturated aliphatic hydrocarbon radical containing from 1 to 4 carbonatoms, R" designates an alkyl radical containing from 1 to 4 carbonatoms, R designates a member selected from the group consisting of themethyl and carboxymethyl radicals, X designates a member selected fromthe group consisting of the bromine, iodine and chlorine atoms and themethyl sulfate radical, such that X designates the chlorine atom when R'designates the carboxymethyl radical, and m designates an integer offrom 1 to 2, said copolymer containing, in polymerized form and on atheoretical monomer basis, from about to about mole percent ofacrylamide and from about 80 to about 5 mole percent of saidethylenically unsaturated sulfine and having a reduced viscosity of fromabout 0.1 to about 5 as measured at a temperature of 30 C. from a 0.5molar aqueous sodium acetate solution containing 0.2 gram of saidcopolymer in milliliters of said solution, which process comprisesreacting said acrylamide in admixture with (a) an alpha-ethylenicallyunsaturated thio-ether of the general formula:

wherein R, R, R" and m are as defined above, and (b) an alkylating agentof the formula R"X wherein R' and X are as defined above, in a ratio offrom about 0.2 to about 20 moles of said 'acrylamide per mole of saidthio-ether and at least about one mole of said alkylating agent perthio-ether radical of said thio-ether, in a solvent selected from thegroup consisting of acetone, acetonitrile and mixtures thereof, at atemperature of from about l0 C. to about C. and in contact with afreeradical polymerization catalyst.

5. The method according to claim 4 wherein the ethylenically unsaturatedthio-ether is 2-methylthioethyl acrylate and wherein the alkylatingagent is dimethyl sulfate.

References Cited by the Examiner UNITED STATES PATENTS 2,540,794 2/1951Otto et a1. 26079.7 2,594,579 4/1952 Novotny et a1. 26079.7 2,874,1312/1959 HWa 260-797 2,885,357 5/1959 Archibald et a1. 21054 2,925,4062/1960 McCurdy 260-797 2,957,821 10/1960 Schifferli 210-54 JOSEPH L.SCHOFER, Primary Examiner.

LEON I. BE'RCOVITZ, Examiner.

D. K. WEDDING, F. L. DENSON, Assistant Examiners.

1. A PROCESS FOR THE PRODUCTION OF A SOLID, GRANULAR HIGH-MOLECULARWEIGHT COPOLYMER OF ACRYLAMIDE AND AN ALPHA-ETHYLENICALLY UNSATURATEDSULFINE OF THE GENERAL FORMULA